Sydney  - Scientists said on Wednesday the dramatic red dust storm that blanketed Sydney two weeks ago provided an unexpected benefit to the environment.

Photographs went around the world of the red dust cloud that enveloped Sydney on September 23, with many saying it looked like the end of the world.

Now scientists monitoring the effect the dust had on Sydney Harbour and the surrounding ocean have discovered nutrients in the topsoil boosted microscopic life in the waters.

This increased carbon capture and showed that increasing nutrients in the ocean could help counter the effects of global warming.

The huge storm carried about 140,000 tons of soil every hour from central Australia across thousands of kilometres to the east coast of Australia.

An estimated 4,000 tons of dust settled on Sydney. Another 3 million tons landed in the Tasman Sea between Australia and New Zealand.

Professor Ian Jones, director of the Ocean Technology Group at the University of Sydney, said the nutrient-rich top soil dumped on Sydney contained up to 1 per cent nutrients such as nitrogen and phosphates.

"After the dust is deposited on the sea surface, the nutrients dissolve in the sunlit region of the ocean and are used by the phytoplankton to multiply," Jones said.

Measurements taken following the dust storm confirmed phytoplankton tripled in Sydney Harbour and in samples taken 10 kilometres offshore.

"We estimate that as a consequence of this, the extra phytoplankton in the Tasman Sea will be capable of capturing 8 million tons of carbon dioxide, about the equivalent of a year's CO2 (carbon dioxide) emissions from a coal-fired one-gigawatt power station," said Jones.

The carbon will slowly sink to the deep ocean in the form of an additional 2 million tonnes of phytoplankton. As the phytoplankton moves through the food chain this will in turn grow extra fish and benefit the fishing industry. (dpa)